Method of applying metal coating to valves



Filed April 27, 1954 FIG? A TTOR/VE Y5 Patented Dec. 6, 1955 [ice METHODOF APPLYING METAL COATING TO VALVES This invention relates generally tomethods of and apparatus for applying metal coatings, but has referencemore particularly to the application oflayers or facings of protectiveheat and wear-resistant metal tothe surfaces of: valves, which, in use,are subjecte'dto high temperatures and abrasive wear.

It 'has heretofore been common practice, in the application of suchmetal to the seat portions of poppet valves; for example, to rotate thevalve at a uniform rate about a vertically-disposed axis, to preheat thearea to be coatedto a'welding temperature by means of gas flames, and tothen progressively deposit the molten protective metal at a uniform rateupon successive portions} of said area while continuing the rotation ofthe valve, said protective metal being derived from the melting ofwelding rods. Such practice is disclosed, by way of example, in WagnerPatent No. 2,301,763.

The aforesaid method is disadvantageous in the following respects: (1)the necessity of rotating each valve as the molten protective metal isapplied requires the use of a great deal of mechanism, including, gears,chains, etc., which are likely to get out of order and requireconsiderable maintenance, (2) the application of protective metal by thegradual melting anddepositin'g, of molten drops upon successive portionsof the annular preheated zone (see lines 55-68, first column, page 3 ofthe Wagner patent) is rather slow and difiicult, particularly from thestandpoint of depositing the metal in uniform, predetermined amounts, itbeing stated in. the Wagner patent that they total time required forpreheating andcoating a valve head about two inches in diameter isapproximately ninety seconds, (3) .the thickness and uniformity of thecoating is extremely difficult. to control, so that a large portion ofthe aforesaid time is taken up .by the necessity of spreading of themolten deposited metal by means of the gas torches subsequent todepositionof the metal (see lines 69-75, first column, page 3, and lines7-12, second column,.page 3 of the Wagner patent), and (4) the fact thatpreheating ofthe area tobe coated to a mere .Welding temperature? is notsufficient to enable production to be speededflupto. anyextent.

The present invention has as its primary object a method of andapparatus for applying protective metal coatings of the aforesaidcharacter, whereby the articles can'be coated at much greater speed thanhas heretofore been possible, and in a much more efficient manner,andwhereb'y the thickness and uniformity of the coating are better'controlled.

Other objects and advantages of the. invention 'will'be apparent duringthe course of the following description.

In the accompanying drawings, forming a part of this specification andin which like numerals are employed to designate like parts throughoutthe same,

Fig. l is a plan view illustrating more or less diagrammatically onetype of apparatus which may be used for practising the invention; I

Fig. 2 is'a cross-sectional view, at approximately. full size scale,taken on theline 22 of Fig. 1;

Fig. 3 is a transverse crossasectional' view, taken on the line 3-3 ofFig. 2, and

Fig. 4 is a transverse crosssectioual view, taken on' the line 4-4 ofFig. 2.

Referring more particularly to the drawings, reference numeral 1designates a circular rotatable platform, which may be rotated by anysuitable mechanism, such, for example, as that disclosed inthe aforesaidWagner patent. The platform 1 is provided at circumferentially spacedpoints with circular recesses 2, in each of which is mounted an annularwork supporting member 3 of heat-refractory material such as Alundum.

Each of the members 3'l1as. an. inwardly and downwardly tapered uppersurface 4 provided. with an. annular step or groove5 therein adjacentthe inner margin adapted to contact a narrow annular portion of the headof a valve 6 of the poppet-type and support said: valve duringapplication of the protective metal onto the annular zone 7 of the valvehead.

As each valve is brought to a position, indicated by reference letter S,and which I shall hereinafter desig mate as the coating station,rotation of' the platform l'is stopped until the coating of the valvehas been completed. Q

When the valve has reached the station S and rotation of the platform 1has been stopped, an applicator head, generally designated by referencenumeral 8, is placed over the valve, as shown in the drawings, and issupported in the position shown until completion of the coating of the'valve; 1' have. not attempted to show means for positioning andsupporting the head 8 during the coating operation, but it will bereadily understood that any suitable mechanism may be provided for thispurpose, and that the positioning, supporting and removal of the headmay be effected automatically, and in syn,- chronism with the movements,of the platform 1.

The applicator head 8 comprises a tubular torch or nozzle 9 providedwith a multiplicity of circumferentiallyspaced passageways 10 extendingthrough the wall thereof parallel with the axis of the nozzle.

Threadedly secured to'the upper end of the nozzle 9 is ahopper'member'll having in its lower end an annular recess or groove 12,which is, in registration withthe upper ends of the passageways 10, andis supplied with a combustible gas mixture through a passageway 13extending radially through the member 11. The passageway 13 is suppliedwith gas by means or" a conduit 14 secured to the member 11;

The inner cylindrical surface 15' of the nozzle 9 is fiush with theinner cylindrical surface 16 of the hopper member 11, and above thesurface 16', the hopper member 11 is provided with an outwardly andupwardly sloping conical surface 17. w Y

The hopper member 11 is provided with a cover or cap 18 having an airvent19, and the cap is provided with an annular flange 20 which is'interiorly threaded for threaded 'securement to the upper end of thehopper member 11.

Secured, as by welding, to the central portion of the lower surface ofthe cap 18 is a tubular member 21 which extends substantially to the"lower end 'of the nozzle 9. The member 21 has a portion 22 of reducedexternal diameter the outer surface of which forms with the surfaces 15and 16 an annular passageway 23, through which powdered metal containedin the hopper 11 may be dropped onto the zone 7' of the valve head.

It may be noted that anannular shoulder 24 is'provided at the upper endof the portion-22- of the'member 21, and that the outer peripheral edgeof this shoulder bears against the surface 17 of the hopper 11 when thecap 18 bears against the upper end 25 of the hopper, so as to stop offflow of the powder into the passageway 22.

When it is desired to feed powder, the cap 18 is unscrewed and theamount of powder fed is controlled by the extent to which the cap isunscrewed. The member 21 thus constitutes a means for controlling orregulating the quantity of powder fed, as well as a passageway for thepowder. a

The protective metals employed for coating the surface 7 of the valveare preferably selected from hard facing high temperature metals, ofwhich those described in Cape Patents 2,396,552; 2,458,502 and2,481,976, are representative. These have melting points in the range2400 F.-2500 F. Another metal which may be used for this purpose is aStellite composition containing 6% cobalt, 30% chromium, and 4 /2%tungsten, with the remainder iron, silicon and manganese, and having amelting point of about 2400 F. These metals are preferably in powderform, and of a mesh or size such that they can flow freely into thepassageway 22.

Before the powder is fed through the passageway 22, and onto the seatportion 7 of the valve, 'the portion 7 is preheated to a temperature atwhich actual melting of said surface occurs. This preheating isaccomplished by igniting the gases issuing from the lower end of thepassageways 10 and causing the flame thus produced to heat the surface 7to the desired temperature. This actual melting of said surface occursat a temperature very close to or approximating the melting temperatureof the valve material.

Since the passageways 10 are uniformly spaced about the valve seat, thesurface 7 is uniformly preheated, without the necessity of rotating thevalve. This eliminates the need for complicated mechanism usuallyprovided for this purpose.

After the surface 7 has been thus preheated, the flame is reduced inintensity, after which powdered metal, in an amount sufficient toprovide the entire hard facing for the valve seat, is dropped throughthe annular passageway 22 onto the surface 7. Since the surface 7 hasbeen heated to a high temperature, the particles of powdered metal willbecome sintered to the surface 7 and to each other, and in order toremelt the particles and cause them to become bonded to the surface 7,the flame is again increased in intensity and continued in operationuntil a coating of uniform character is formed. Since the powdered metalis uniformly distributed about the valve seat, and is uniformly heatedthroughout the circumference of the valve seat, it is unnecessary torotate the valve in order to obtain such uniform distribution.

The method, as described, is also advantageous in that it takesconsiderably less time to coat the valves than is required in the Wagnermethod, and the thickness and uniformity of the coating is controlled ina more desirable manner. Moreover, no excess coating metal is formed,which requires removal by costly grinding operations.

Instead of rotating the platform 1 to the station S, the platform may bestationary, and the applicator head moved into position over the valvessuccessively. Moreover, a plurality of applicator heads may be provided,so that coating of all of the valves on the platform may be accomplishedsimultaneously. In this latter case, a single hopper for all of theapplicator heads may be provided, as Well as a single source of gas forall of the heads, thereby enabling production to be greatly speeded.

It may be noted that if desired, the valves may be individually rotatedabout their own axes during coating, since the apparatus and methoddescribed do not preclude such a possibility.

It is to be understood that various changes may be made in the methodand apparatus herein specifically described without departing from thespirit of the invention or the scope of the appended claims.

Having thus described my invention, I claim:

1. The method of providing the wearing surface of valves and similararticles with welded-on facings of a protective metal, which comprisessupporting a poppettype valve along an annular zone at the margin of thevalve head, said valve head having an annular seating surface facing inan upward direction and supported at an acute angle to the horizontal,uniformly preheating said valve to raise said seating surface to anelevated temperature at which actual melting of said surface occurs,thereafter depositing powdered facing metal selected from hard-facing,high temperature metals which have melting points in excess of about2400 F. substantially uniformly about said seating surface, and thenheating said powdered metal to cause it to become fused and bonded tosaid seating surface and be uniformly distributed thereover.

2. The method, as defined in claim 1, in which said powdered metal isfed directly onto said surface in a substantially annular stream of adiameter corresponding substantially to the diameter of said seatingsurface.

3. The method, as defined in claim 1, in which said preheating isaccomplished by means of gas flames playing simultaneously on the entireseating surface.

4. The method of providing the wearing surface of valves and similararticles with welded-on facings of a protective metal, which comprisessupporting a poppettype valve along an annular zone at the margin of thevalve head, said valve head having an annular seating surface facing inan upward direction and supported at an acute angle to the horizontal,uniformly preheating the valve, while stationary, to raise the entireseating surface simultaneously to a temperature approximating themelting point of the valve material, thereafter depositing upon saidsurface, in a single operation, and in an annular stream, only asufficient amount of powdered facing metal selected from hard-facing,high temperature metals which have melting points in excess of about2400 F. to provide said welded-on facing, and then heating said powderedmetal to cause it to become fused and bonded to said seating surface andto be uniformly distributed thereover.

5. The method, as defined in claim 4, in which said annular stream is ofa diameter corresponding substantially to the diameter of said seatingsurface.

6. The method, as defined in claim 4, in which said preheating isaccomplished by means of gas flames play ing simultaneously on theentire seating surface, and said fusion of the facing metal is likewiseaccomplished by means of gas flames playing simultaneously on all partsof the facing metal.

7. The method, as defined in claim 4, in which the powdered facing metalis selected from metals having melting points in the range of from about2400 F. to about 2500 F.

References Cited in the file of this patent UNITED STATES PATENTS701,298 Cowper-Coles June 3, 1902 806,900 Leonard Dec. 12, 1905 933,725Schroeder Sept. 7, 1909 1,244,414 Bernheim Oct. 23, 1917 2,277,571Wagner Mar. 24, 1942 2,301,763 Wagner Nov. 10, 1942 2,326,403 SnyderAug. 10, 1943 2,354,113 Gould July 18, 1944 2,358,090 Longoria Sept. 12,1944

1. THE METHOD OF PROVIDING THE WEARING SURFACE OF VALVES AND SIMILARARTICLES WITH WELDED-ON FACINGS OF A PROTECTIVE METAL, WHICH COMPRISESSUPPORTING A POPPETTYPE VALVE ALONG AN ANNULAR ZONE AT THE MARGIN OF THEVALVE HEAD, SAID VALVE HEAD HAVING AN ANNULAR SEATING SURFACE FACING INAN UPWARD DIRECTION AND SUPPORTED AT AN ACUTE ANGLE TO THE HORIZONTAL,UNIFORMLY PREHEATING SAID VALVE TO RAISE SAID SEATING SURFACE TO ANELEVATED TEMPERATURE AT WHICH ACTUAL MELTING OF SAOD SURFACE OCCURS,THEREAFTER DEPOSITING POWDERED FACING METAL SELECTED FROM HARD-FACING,HIGH TEMPERATURE METALS WHICH HAVE MELTING POINTS IN EXCESS OF ABOUT2400*F. SUBSTANTIALLY